Staple gun



FIG. 1 is a front, left-side perspective view of a staple gun showing the new design;

FIG. 2 is a right side view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a front view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken line showing in FIGS. 1, 2, 3, 4 and 7 is for the purpose of illustration and forms no part of the claimed design. 

CLAIM The ornamental design for a staple gun, as shown and described. 